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442 lines
13 KiB
442 lines
13 KiB
# ext/declarative/clsregistry.py
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# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: https://www.opensource.org/licenses/mit-license.php
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"""Routines to handle the string class registry used by declarative.
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This system allows specification of classes and expressions used in
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:func:`_orm.relationship` using strings.
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"""
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import weakref
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from . import attributes
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from . import interfaces
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from .descriptor_props import SynonymProperty
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from .properties import ColumnProperty
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from .util import class_mapper
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from .. import exc
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from .. import inspection
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from .. import util
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from ..sql.schema import _get_table_key
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# strong references to registries which we place in
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# the _decl_class_registry, which is usually weak referencing.
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# the internal registries here link to classes with weakrefs and remove
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# themselves when all references to contained classes are removed.
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_registries = set()
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def add_class(classname, cls, decl_class_registry):
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"""Add a class to the _decl_class_registry associated with the
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given declarative class.
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"""
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if classname in decl_class_registry:
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# class already exists.
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existing = decl_class_registry[classname]
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if not isinstance(existing, _MultipleClassMarker):
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existing = decl_class_registry[classname] = _MultipleClassMarker(
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[cls, existing]
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)
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else:
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decl_class_registry[classname] = cls
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try:
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root_module = decl_class_registry["_sa_module_registry"]
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except KeyError:
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decl_class_registry[
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"_sa_module_registry"
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] = root_module = _ModuleMarker("_sa_module_registry", None)
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tokens = cls.__module__.split(".")
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# build up a tree like this:
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# modulename: myapp.snacks.nuts
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#
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# myapp->snack->nuts->(classes)
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# snack->nuts->(classes)
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# nuts->(classes)
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#
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# this allows partial token paths to be used.
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while tokens:
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token = tokens.pop(0)
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module = root_module.get_module(token)
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for token in tokens:
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module = module.get_module(token)
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module.add_class(classname, cls)
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def remove_class(classname, cls, decl_class_registry):
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if classname in decl_class_registry:
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existing = decl_class_registry[classname]
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if isinstance(existing, _MultipleClassMarker):
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existing.remove_item(cls)
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else:
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del decl_class_registry[classname]
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try:
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root_module = decl_class_registry["_sa_module_registry"]
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except KeyError:
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return
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tokens = cls.__module__.split(".")
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while tokens:
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token = tokens.pop(0)
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module = root_module.get_module(token)
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for token in tokens:
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module = module.get_module(token)
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module.remove_class(classname, cls)
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def _key_is_empty(key, decl_class_registry, test):
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"""test if a key is empty of a certain object.
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used for unit tests against the registry to see if garbage collection
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is working.
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"test" is a callable that will be passed an object should return True
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if the given object is the one we were looking for.
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We can't pass the actual object itself b.c. this is for testing garbage
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collection; the caller will have to have removed references to the
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object itself.
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"""
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if key not in decl_class_registry:
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return True
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thing = decl_class_registry[key]
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if isinstance(thing, _MultipleClassMarker):
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for sub_thing in thing.contents:
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if test(sub_thing):
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return False
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else:
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return not test(thing)
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class _MultipleClassMarker(object):
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"""refers to multiple classes of the same name
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within _decl_class_registry.
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"""
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__slots__ = "on_remove", "contents", "__weakref__"
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def __init__(self, classes, on_remove=None):
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self.on_remove = on_remove
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self.contents = set(
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[weakref.ref(item, self._remove_item) for item in classes]
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)
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_registries.add(self)
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def remove_item(self, cls):
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self._remove_item(weakref.ref(cls))
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def __iter__(self):
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return (ref() for ref in self.contents)
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def attempt_get(self, path, key):
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if len(self.contents) > 1:
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raise exc.InvalidRequestError(
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'Multiple classes found for path "%s" '
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"in the registry of this declarative "
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"base. Please use a fully module-qualified path."
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% (".".join(path + [key]))
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)
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else:
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ref = list(self.contents)[0]
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cls = ref()
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if cls is None:
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raise NameError(key)
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return cls
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def _remove_item(self, ref):
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self.contents.discard(ref)
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if not self.contents:
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_registries.discard(self)
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if self.on_remove:
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self.on_remove()
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def add_item(self, item):
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# protect against class registration race condition against
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# asynchronous garbage collection calling _remove_item,
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# [ticket:3208]
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modules = set(
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[
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cls.__module__
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for cls in [ref() for ref in self.contents]
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if cls is not None
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]
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)
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if item.__module__ in modules:
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util.warn(
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"This declarative base already contains a class with the "
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"same class name and module name as %s.%s, and will "
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"be replaced in the string-lookup table."
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% (item.__module__, item.__name__)
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)
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self.contents.add(weakref.ref(item, self._remove_item))
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class _ModuleMarker(object):
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"""Refers to a module name within
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_decl_class_registry.
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"""
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__slots__ = "parent", "name", "contents", "mod_ns", "path", "__weakref__"
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def __init__(self, name, parent):
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self.parent = parent
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self.name = name
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self.contents = {}
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self.mod_ns = _ModNS(self)
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if self.parent:
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self.path = self.parent.path + [self.name]
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else:
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self.path = []
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_registries.add(self)
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def __contains__(self, name):
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return name in self.contents
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def __getitem__(self, name):
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return self.contents[name]
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def _remove_item(self, name):
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self.contents.pop(name, None)
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if not self.contents and self.parent is not None:
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self.parent._remove_item(self.name)
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_registries.discard(self)
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def resolve_attr(self, key):
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return getattr(self.mod_ns, key)
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def get_module(self, name):
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if name not in self.contents:
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marker = _ModuleMarker(name, self)
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self.contents[name] = marker
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else:
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marker = self.contents[name]
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return marker
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def add_class(self, name, cls):
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if name in self.contents:
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existing = self.contents[name]
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existing.add_item(cls)
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else:
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existing = self.contents[name] = _MultipleClassMarker(
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[cls], on_remove=lambda: self._remove_item(name)
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)
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def remove_class(self, name, cls):
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if name in self.contents:
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existing = self.contents[name]
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existing.remove_item(cls)
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class _ModNS(object):
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__slots__ = ("__parent",)
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def __init__(self, parent):
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self.__parent = parent
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def __getattr__(self, key):
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try:
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value = self.__parent.contents[key]
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except KeyError:
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pass
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else:
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if value is not None:
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if isinstance(value, _ModuleMarker):
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return value.mod_ns
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else:
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assert isinstance(value, _MultipleClassMarker)
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return value.attempt_get(self.__parent.path, key)
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raise NameError(
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"Module %r has no mapped classes "
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"registered under the name %r" % (self.__parent.name, key)
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)
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class _GetColumns(object):
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__slots__ = ("cls",)
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def __init__(self, cls):
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self.cls = cls
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def __getattr__(self, key):
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mp = class_mapper(self.cls, configure=False)
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if mp:
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if key not in mp.all_orm_descriptors:
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raise AttributeError(
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"Class %r does not have a mapped column named %r"
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% (self.cls, key)
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)
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desc = mp.all_orm_descriptors[key]
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if desc.extension_type is interfaces.NOT_EXTENSION:
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prop = desc.property
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if isinstance(prop, SynonymProperty):
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key = prop.name
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elif not isinstance(prop, ColumnProperty):
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raise exc.InvalidRequestError(
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"Property %r is not an instance of"
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" ColumnProperty (i.e. does not correspond"
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" directly to a Column)." % key
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)
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return getattr(self.cls, key)
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inspection._inspects(_GetColumns)(
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lambda target: inspection.inspect(target.cls)
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)
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class _GetTable(object):
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__slots__ = "key", "metadata"
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def __init__(self, key, metadata):
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self.key = key
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self.metadata = metadata
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def __getattr__(self, key):
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return self.metadata.tables[_get_table_key(key, self.key)]
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def _determine_container(key, value):
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if isinstance(value, _MultipleClassMarker):
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value = value.attempt_get([], key)
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return _GetColumns(value)
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class _class_resolver(object):
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__slots__ = (
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"cls",
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"prop",
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"arg",
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"fallback",
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"_dict",
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"_resolvers",
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"favor_tables",
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)
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def __init__(self, cls, prop, fallback, arg, favor_tables=False):
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self.cls = cls
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self.prop = prop
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self.arg = arg
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self.fallback = fallback
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self._dict = util.PopulateDict(self._access_cls)
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self._resolvers = ()
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self.favor_tables = favor_tables
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def _access_cls(self, key):
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cls = self.cls
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manager = attributes.manager_of_class(cls)
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decl_base = manager.registry
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decl_class_registry = decl_base._class_registry
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metadata = decl_base.metadata
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if self.favor_tables:
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if key in metadata.tables:
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return metadata.tables[key]
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elif key in metadata._schemas:
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return _GetTable(key, cls.metadata)
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if key in decl_class_registry:
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return _determine_container(key, decl_class_registry[key])
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if not self.favor_tables:
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if key in metadata.tables:
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return metadata.tables[key]
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elif key in metadata._schemas:
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return _GetTable(key, cls.metadata)
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if (
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"_sa_module_registry" in decl_class_registry
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and key in decl_class_registry["_sa_module_registry"]
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):
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registry = decl_class_registry["_sa_module_registry"]
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return registry.resolve_attr(key)
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elif self._resolvers:
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for resolv in self._resolvers:
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value = resolv(key)
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if value is not None:
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return value
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return self.fallback[key]
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def _raise_for_name(self, name, err):
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util.raise_(
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exc.InvalidRequestError(
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"When initializing mapper %s, expression %r failed to "
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"locate a name (%r). If this is a class name, consider "
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"adding this relationship() to the %r class after "
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"both dependent classes have been defined."
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% (self.prop.parent, self.arg, name, self.cls)
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),
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from_=err,
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)
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def _resolve_name(self):
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name = self.arg
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d = self._dict
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rval = None
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try:
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for token in name.split("."):
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if rval is None:
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rval = d[token]
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else:
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rval = getattr(rval, token)
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except KeyError as err:
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self._raise_for_name(name, err)
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except NameError as n:
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self._raise_for_name(n.args[0], n)
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else:
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if isinstance(rval, _GetColumns):
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return rval.cls
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else:
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return rval
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def __call__(self):
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try:
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x = eval(self.arg, globals(), self._dict)
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if isinstance(x, _GetColumns):
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return x.cls
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else:
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return x
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except NameError as n:
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self._raise_for_name(n.args[0], n)
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_fallback_dict = None
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def _resolver(cls, prop):
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global _fallback_dict
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if _fallback_dict is None:
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import sqlalchemy
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from sqlalchemy.orm import foreign, remote
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_fallback_dict = util.immutabledict(sqlalchemy.__dict__).union(
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{"foreign": foreign, "remote": remote}
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)
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def resolve_arg(arg, favor_tables=False):
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return _class_resolver(
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cls, prop, _fallback_dict, arg, favor_tables=favor_tables
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)
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def resolve_name(arg):
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return _class_resolver(cls, prop, _fallback_dict, arg)._resolve_name
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return resolve_name, resolve_arg
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